Mixing devices are in wide use in industry. For example, a large number of applications in industries such as pharmaceuticals, food processing, chemical processing, and other industries often use a mixing device which includes a vessel for containing the material to be mixed, and a typically vertical agitator shaft that is driven by a motor and has radially extending impellers.
In some of these arrangements, the vertical agitator shaft is a multi-piece shaft having a top shaft driven by a motor and gearbox or speed reducer, connected to one or more intermediate impeller shafts with radial impellers, and a lower or bottom shaft. Often, the vertical agitator shaft projects downwards from the top of the vessel and at its lower end is supported by a so-called steady bearing or foot bearing. The foot bearing typically includes some form of bushing arrangement that is attached to the lower end of the shaft to resist side loads on the shaft.
The above mentioned conventional foot-type steady bearing designs are effective, but have some disadvantages however. In particular, some industries require highly sanitary operating conditions and cleanability. The presently known steady foot bearing designs suffer from the disadvantages that they typically have numerous horizontal surfaces, unsealed cavities, exposed threaded connections, and other difficult to clean surfaces and components.
Another difficultly with the present designs is that replacement of the bushing wear parts can generally not be accomplished without significant vertical adjustment of the agitator shaft, thus undesirably requiring partial disassembly of the rest of the mixer, including the top seal.
Yet another disadvantage of the existing designs is that during repair or maintenance of the top seal arrangement, these designs may not have the ability to support the bottom of the agitator shaft, and therefore support of the agitator shaft is required from the top during these changes.
Accordingly, there is a need in the art for an improved sanitary steady bearing and method which provides for sanitary characteristics, easy cleanability, and easy replacement of wear parts without disassembling the rest of the agitator, and which can also support the agitator shaft during seal changes.